The beach at Warren Dunes is wide, clean, and backed by dunes rather than flat parkland, which gives it a more dramatic feel than most Great Lakes beaches. The water is freshwater, so there is no salt and no tides, but Lake Michigan is large enough to generate real waves — especially in summer when southwest winds pick up in the afternoon. On calm mornings the lake is glassy and cold and perfect; by midday it is usually warmer and choppy, which is when most people are in it. Shorebirds, including great blue herons, work the waterline in the early morning before the crowds arrive.
This is the main reason Chicago day-trippers make the drive, and on a hot weekend in July the parking lot fills early. Arriving before 10am gives you a decent spot and a quieter beach. Dogs are not allowed on the beach, though they can come on the trails. There are no alcohol sales or consumption allowed anywhere in the park, so plan accordingly. The swimming is unsupervised — there are no lifeguards — and the drop-off from the sandbar can be abrupt, so be cautious with young children in deeper water.